1. Field of the Invention
The invention relates to the repair of building foundations by underpinning. More specifically, it relates to a method for aligning pile segments during installation, inspecting pile penetration depth, and continuously reinforcing an improved segmental precast concrete pile used for underpinning repairs.
2. Related Art
Precast concrete pile segments are used in the underpinning of building foundations comprising vertically stacked, unconnected, precast concrete segments. These segments are pressed or driven vertically into the soil one at a time until adequate load capacity is obtained. This system came into favor because it required low clearance under the structure being leveled and did not require a predrilled hole, with concurrent hauling of removed dirt and pouring of cement. Poured cement piers can leave a structure and the surrounding lawns in disrepair for several weeks because of the curing time. Similarly, a one piece precast concrete pile is rarely used for underpinning because it requires heavy equipment to install, and is impossible to install beneath an existing building without requiring an exorbitant amount of demolition to provide adequate clearance. The stacked precast segments pile has several significant disadvantages the principal one being that the pile segments are not aligned, other than being stacked on each other, and detrimental misalignments can occur.
U.S. Pat. No. 5,288,175 addressed the deficiencies with a precast concrete starter segment with a high strength steel strand extending from its center and precast concrete pile segments constructed with strand ways which are threaded onto the steel strand and aligned for installation in the same manner as the starter segment. This pile is wholly dependent on the steel cable for alignment. The high strength steel is subject to highly corrosive conditions from the concrete and the soil and special procedures such as the use of construction adhesives to bond and seal the cable and the segments or the use of stainless steel. If the cable fails, this system is little better than the prior unconnected segments.